In recent years, wider use of an electric vehicle and a plugin hybrid vehicle is desired due to growing global environmental consciousness. In these vehicles, a main battery is mounted to supply power to motors while the vehicle is running. In order to safely charge the main battery with lesser power when being charged from a commercial AC power source, there is a need to mount a power source device which has a function of insulating the commercial power from the main battery. The power source device is required to achieve a high conversion efficiency. PTL 1 discloses a resonance charging device which is provided with an AC-DC converter and a resonance DC-DC converter, and aimed at improvement in conversion efficiency by increasing an input voltage of the resonance DC-DC converter as well as an increase of a battery voltage.
In addition, in these vehicles, an insulated DC-DC converter is mounted to supply power from the main battery to accessory system loads of electrical components while the vehicle is running.